The general aim of this research is to delineate the various steps in the glycosylation of proteins and to determine possible biological consequences of impaired glycosylation. Our approach is to isolate and characterize mammalian cell mutants defective in glycosylation. Chinese hamster ovary (CHO) cell mutants are isolated by both single-\and multistep selection procedures and by screening procedures. Once isolated, the enzymatic defect in the cell line is determined, allowing us to catalog various reactions in the synthetic pathway; subsequently, we can determine what effect the alteration in a particular reaction has on different glycoprotein products. For example, we previously determined that both the cells and membrane preparations of a concanavalin A-resistant CHO cell line (B211)\failed to glucosylate its oligosaccharide-lipid intermediates and protein. As a result, B211 cells synthesized lysosomal enzymes of an altered structure, containing complex oligosaccharides rather than phosphorylated, high-mannose ones. Total acid hydrolase activity was diminished and the residual activity was secreted rather than sequestered in the lysosome.